Combustion process and apparatus



March 21, 1%? P. H. KYDD COMBUSTION PROCESS AND APPARATUS File d March 11, 1965 2 Sheets-Sheet l (Pr/0r Ari) hum/#0,: Pau/ H Kyod,

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March 21, 1967 P. H. KYDD COMBUSTION PROCESS AND APPARATUS 2 Sheets-Sheet 2 Filed March 11, 1965 0 ry m r 8 w W P w W 6 y w a 4 b 3 \\n 5 F A\ w 2 5 United States l atent )fiice assists Patented Mar. 21, 196i 3,309,866 COMBUSTIGN PROCESS AND APPARATUS Paul H. Kydd, Scotia, N.Y., assignor to General Electric Company, a corporation of New York Filed Mar. 11, 1965, Ser. No. 439,020 17 Claims. (Cl. 60-39.02)

This invention relates to a gas phase combustion of fuels and more particularly to a process and apparatus for the conduct of flameless gas phase combustion.

In conventional combustion applications, flame propagation has been a requisite, and this requisite has dictated the necessity of maintaining minimum burned gas temperatures ranging from about 1000 to about 1200 C. However, such gas temperatures are often inconvenient in practical combustion structures. For example, gas turbines require a turbine inlet temperature considerably below the temperature at which hydrocarbons will burn with flame combustion. As a result, the technique that has been employed in the past has been to divide the combustion process into a reaction stage and a dilution stage, the reaction stage to burn the fuel and the dilution stage to cool the gas to turbine inlet temperature. Such an arrangement considerably complicates the combustion process and the combustion apparatus. Also, although it is frequently desirable to be 'able to burn very dilute fuel mixtures, such as occur as process wastes, in order to recover the heat value contained therein, conventional gas turbines are unable to utilize poor quality gaseous fuels to produce power directly therefrom.

In order to more clearly understand this invention certain technical terms used in the description of the inventtion are defined as follows:

The term recirculation refers to the combining of hot substantially completely burned gas within a gas turbine combustor with the mixture of fuel and air entering the combustor in a manner producing very effective mixing thereof and heat exchange therebetween to enable the production of power directly therefrom. This term is to be distinguished from the process of adding air to hot incompletely burned engine exhaust or to waste gases of various industrial processes The term gases in addition to true gases is also intended to include vapors.

Burning or combustion refers to the oxidation of a fuel to convert its chemical energy to thermal energy.

Flame or flame front are terms describing the thin region, which can propagate into a flammable mixture of fuel and air due to the extremely high rate of the combustion reaction within the region. Characteristically the reactions in flame fronts must take place in time periods measured in milliseconds.

Flarneless combustion is the phenomenon of the occurrence of combustion reactions uniformly throughout the volume of a combustor. This type of combustion may be employed with fuel-air proportions outside the normal flammability limits and/ or at burned gas temperatures too low to support a self-propagating flame front. Thus, the restriction of time for conduct of the reaction is relaxed completely.

Scientific investigations have shown that homogeneous oxidation of various mixtures of gases may be effected outside the normal flammability limits of such gases. Such investigations have been directed toward the investigation of explosion limits of hydrogen and carbon monoxide or of cool flames and associated phenomena in connection with hydrocarbons. Although, this phenomenon has been known, there have not heretofore been developed any means or processes whereby flameless gas phase combustion has been applied to the production of power.

It is therefore a primary object of this invention to provide a gas turbine construction of simpler, more economical design and operation.

Another prime object of this invention is the provision of a method of operating a gas turbine apparatus whereby a uniform temperature distribution at the turbine inlet of the apparatus is achieved without raising the temperature anywhere in the combustor above the turbine inlet temperature.

It is another object of this invention to provide in an economical manner conditions suitable for the flameless combustion of non-flammable gas mixtures at rates high enough to extend the capability of gas turbine combustion equipment to the generation of power from poor quality, or very dilute, fuels.

It is still another object of this invention to provide in a gas turbine combustor for the mixing of incoming unburned fuel and air mixture with hot burned gas in sufficient volume to carry the oxidation reaction of the incoming mixture to completion, even though the rate of burning is not high enough to maintain a flame front anywhere in the mixture.

It is still a further object of this invention to provide in a gas turbine combustor for means for mixing sufficient volumes of hot burned gas with an incoming unburned mixture of fuel and air to raise the temperature of the mixture to a point at which an oxidation reaction will commence (about 550 C. or higher, depending on the type of fuel) without changing the burned gas temperature.

It is yet another object of this invention to provide in a gas turbine combustor for recirculation means for mixing sufiicient volumes of hot burned gas with an incoming unburned mixture of fuel and air to raise the temperature of the mixture to a point at which the oxidation reaction will commence without changing the burned gas tempera- V ture.

The above and other objects are accomplished in the practice of this invention in gas turbine construction wherein fuel is added directly to the inlet air by means of a low pressure fuel injection means, such as a simple carburetor unit, and the mixture is passed first to a compressor and then radially outward through a diffuser to enter around the inner circumference of a toroidally shaped recirculating combustor retaining a considerable amount of its energy in kinetic form, which results in movement of the mixture in a pronounced whirling course. Entry of the mixture at high velocity (at least about feet per second) into the combustor promotes mixing of the gas input with the gas already in the combustor and the whirling motion of this input gas mixture sustains whirling motion of the entire gas content of the combustor. By these two mechanisms recirculation is accomplished as the incoming mixture is added to and thoroughly mixed with similarly'whirling substantially completely burned gas. Although the incoming unburned mixture is considerably diluted by the burned gas this dilution only reduces the rate of oxidation of the gross gas mixture in proportion to the dilution ratio, and since a very rapid rise in thetemperature occurs in the gross gas mixture, which temperature rise increases the rate of oxidation exponentially, the net result is a substantial increase in the oxidation rate so that at a temperature between about 800 and 900 C. burning of the Weak gross gas mixture proceeds as flameless combustion throughout the combustor.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing in which:

FIG. 1 schematically illustrates the essential elements of a prior art gas turbine construction;

FIG. 2 is a schematic illustration of a preferred gas turbine construction embodying combustor construction in accordance with this invention whereby the mixture of air and fuel enters the combustor all around its inner periphery, moves in the whirling pattern generally represented by the arrows, becomes thoroughly mixed with and heated by the hot whirling burned gases and is oxidized at a rapid rate without reliance upon flame front generation or maintenance; and

FIG. 3 discloses the design of a second embodiment of a gas turbine having combustor construction embodying this invention and illustrates a simple low pressure fuel injection means in combination therewith.

The gas turbine shown schematically in FIG. 1 is constructed in accordance with the principles of power lant design disclosed in U.S. Patent No. 2,601,000A. J. Nerad. Centrally-located compressor 11 receives air only, raises the pressure of this air to the operating level and discharges the compressed air into annular plenum 12 through annular diffuser 13. A number of individual combustion cans or units 14 are spaced circumferentially around within the annular plenum 12 with the outlets 16 thereof connected to the annular nozzle box of turbine 17 around its periphery. The compressed air in plenum 12 enters combustion unit 14 through holes 18; fuel is sprayed into the interior of combustion unit 14 from nozzle 19, and the fuel-air mixture is ignited with an ignition device, such as spark plug 12. Within combustion unit 14 two zones are created and maintained; the primary zone 20 adjacent fuel nozzle 19 is a region of turbulent flow, which serves to maintain flame combustion, while the secondary zone 20a is a region wherein cooler air is mixed with the hot combustion gases thereby cooling these gases to a temperature suitable for entry into the turbine 17. In such a construction a flame front :must be maintained and, if the flame is blown out, combustion ceases.

Since the gas temperature allowable for entry of the combustion products into the turbine 17 is considerably lower than the temperature of the gases in the primary zone, it is difficult to maintain uniform temperature distribution at the turbine inlet and non-uniformity of turbine inlet temperature distribution diminishes the operating efiiciency of the power plant.

In contrast to this conventional combustor construction in which fuel must be injected into the combustor unit itself in order to maintain the requisite flame front and wherein as a consequence temperature gradients of considerable magnitude occur in the combustor unit, this invention successfully achieves uniform temperature distribution at the turbine inlet using flameless combustion in the combustor unit, which combustion reaction proceeds at a rapid rate with the temperature in all parts of the combustor unit, however, remaining at or below the turbine inlet temperature. This feature will permit use of a higher turbine inlet temperature and/or result in longer useful turbine life.

A preferred embodiment of this invention is shown in FIG. 2. The recirculating gas turbine 30 comprises axial compressor 31, which receives an air and fuel mixture (as from a simple carburetor, not shown) at low pressure, raises the pressure thereof to the operating level and discharges the compressed mixture via diffuser section 32 into the combustor 33, which is toroidal in shape. Preferably the entry for the incoming fluid mixture and the exit for the combustion gases to the turbine 34 are tangential to the curved wall, or shell, 35 of combustor 33. To insure the continued whirling motion of the incoming mixture the annular plate 36 (extension of diffuser section 32) projects into the interior of combustor 33 in the manner shown. The recirculation action (the mixing of the incoming mixture and the burned gases) is encouraged by the location of holes 37 spaced around the inner periphery of annular plate 36. Thus, between having the holes 37 located at a region 32a of low pressure and having the outer periphery of plate 36 defining with the wall 35 of combustor 33 a higher pressure region 32b, this differential in pressure serves to promote the recirculation so vital to establishing the rate of flameless combustion required for power generation.

With this arrangement an incoming air-fuel mixture is compressed and passed to combustor 33. This incoming compressed mixture will usually have a temperature in the range of from about to about 350 C. depending upon the compression ratio. Upon exposure to the substantially completely burned gas still whirling in combustor 33, a thorough mixing (recirculation) of the whirling incoming mixture and the whirling burned gas occurs. This recirculation results in rapid raising of the temperature of the now diluted incoming mixture. With the rise in temperature an oxidation reaction will commence, usually at about 550 C. or higher, and as the temperature continues to increase burning by flameless combustion will proceed at a rapid rate at temperatures in ranges of SOD-900 C.

By use of this mode of combustion, reliance upon a flame front with the disadvantages thereof is avoided and a combustor of greatly simplified construction may be employed. As is the case with conventional gas turbines an auxiliary power source is used to operate the compressor in starting the unit. Even though it is generally advantageous to provide in the combustion 33 an ignition means comprising a fuel nozzle-ignition plug combination 38, use of this device is discontinued immediately after suflicient hot burned gas is generated in the combustor 33 to enable the establishment of effective recirculation for initiating normal flameless operation. Also if desired, layer 39 of appropriate solid insulation may be applied over the exterior of confining wall 35 to reduce heat losses from the combustion volume and thereby reduce the amount of fuel required to achieve a given burned gas temperature.

In a flameless combustor of the proper shape and/or design to provide recirculation using hydrocarbon fuels and at a burned gas temperature of about 900 C., the volume necessary in the combustor may be calculated from the fact that the residence time required in the combustor ranges from about 0.5 second to about 0.1 second at the design flow rate and these values are substantially independent of pressure.

Power output from a gas turbine of the improved type disclosed herein can be controlled by throttling (as in the manner of control with reciprocating engines). Such control is easy to accomplish and will provide better part-load performance because of reduced compressor and turbine losses at reduced flow and because the turbine inlet temperature is held constant. Pressure drop through the combustor portion of the gas turbine is negligible, because it is no longer necessary to dilute the burned gas with air to reduce its temperature to turbine inlet temperature as is required in the case of flame combustion.

Still another embodiment of this invention is illustrated in FIG. 3. Therein, in gas turbine 40, disc 41 accommodates both centrifugal compressor 42 and radial inflow turbine 43. Shaft 44 transmits the power generated to the load. In such a construction, the turbine 43 is cooled partly by the conduction of heat through disc 41 toward the compressor side thereof and partly by cooling air flow, which passes over the outer turbine disc 46, as shown by the arrows. This cooling mechanism permits the use of relatively high turbine inlet temperatures. Additional cooling can be provided by adding liquid fuel, rather than gaseous fuel, directly to the air entering via inlet 47 through carburetor 48. Utilizing this manner of fuel feed enables elimination of the high pressure spray injectors ordinarily employed in conventional gas turbines and provides the additional advantage that evaporation of the liquid fuel precools the incoming air allowing higher pressure ratios to be employed in a simple compressor by the use of less compressor power. Also, the addition of liquid fuel in this manner will help remove heat being conducted from the turbine via disc 41 without degrading compressor performance. If desirable, water injection into the incoming fuel-air mixture may be employed to maximize all the foregoing advantages.

The compressed mixture of fuel and air passes from compressor 42 to recirculating combustor 49. The shape and the volume of the combustor 49 is important to permit both the generation and maintenance of recirculation flow. The volume of combustor 49 will be larger than conventional combustors handling comparable throughputs of air flow.

The requisite flow pattern for the promotion and maintenance of recirculation is provided in large part by the design of the diflFuser 51, which leaves enough kinetic energy in the fuel-air mixture to sustain whirling flow of the contents of the combustor 49 after a substantially tangential entry thereto as shown by the arrows. As in the embodiment in FIG. 2 this whirling action provides the recirculation action whereby the incoming fuel-air mixture becomes thoroughly mixed with hot substantially completely oxidized gas and thereupon the flameless combustion proceeds. Alternately means for further promoting recirculation as disclosed in the embodiment of FIG. 2 may be employed, of course.

Starting is accomplished by cranking the compressor and by admitting a rich fuel-air mixture to combustor 49 with an appropriate choke (not shown) setting. This rich mixture is ignited with spark plug 52, or similar igniter, to provide hot burned gases in combustor 49. Thereafter, the entering whirling air-fuel mixture will thoroughly mix with the burned gases in the nature of a well stirred reactor thereby initiating the flameless combustion as described above, whereupon the spark plug 52 is no longer required and the leaner fuel-air mixture is relied upon for normal operation. The layer 53 of solid insulation may be employed to minimize heat losses to the large interior surface area of combustor 49.

The embodiment shown in FIG. 3 is particularly useful when liquid fuels are employed, while the embodiment of FIG. 2 is preferred for use with gaseous fuels, such as the poor quality gases produced as process wastes. Such poor quality gasses cannot form a true flame and it is only with the advent of this invention sucessfully employing flameless combustion that this source can be realized in the direct production of power.

With either of the embodiments illustrated (FIGS. 2 and 3) poor quality gases may be employed as fuel and burned to a final oxidation temperature of from about 800 to 900 C. at which temperature the rate of heat release is of the order of 3x10 B.t.u./hr. cu. ft. at 1 atmosphere and proportionately higher at higher pressures.

Because the temperature resulting from the flameless combustion is also the turbine inlet temperature, no liners are required in order to add diluent air to combustion products prior to passage to the turbine. Also, with this invention when gaseous fuel is employed it is no longer necessary to compress the fuel and air separately as is required in conventional gas turbines and the mixing of the fuel and air before compression results in a uniform mixture Without hazard, because such mixtures are well outside the flammability limits.

It is, of course, possible that the fuel to be used is already at an elevated pressure, is very hot or is very dirty. In such a case it would be uneconomical or impractical to allow such fuel to pass through the compressor and this invention is flexible enough to utilize such fuels by admittin this fuel to the system at the diffuser at the appropriate pressure for conduct into the combustor at high velocity by the compressed air for flameless combustion therein. In special cases in which it is required to bleed clean air from the compressor, as to pressurize the cabin of an aircraft, a similar expedient may be necessary.

A further application for this invention is in the burning of slightly dirty gas, such as is encountered in a coal gasifier combined cycle plant. One serious technical problem in the development of such a coal gasifier combined cycle plant is that if the nearly clean gas from the gas producer "unit is burned in a conventional gas turbine power generating apparatus, the residual ash is raised to its fusion point momentarily (during the burning operation before the combustion gases are diluted to the turbine inlet temperature) in which condition it may then agglomerate on surfaces Within the apparatus. Later the agglomerated material will break off in large pieces, which are destructive to the turbine. When such slightly dirty gas is oxidized by flameless combustion, the temperature in the combustor cannot rise above turbine inlet temperature so that the ash will never be softened and the destructive agglomeration and detachment will not occur.

Various modifications are contemplated and may obviously be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter defined by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A power plant comprising in combination,

(a) a compressor,

(1) said compressor having circumfereutially disposed outlet means and having inlet means for receiving the combustion air input to said power plant,

(b) means connected to said inlet means for injecting fuel into said inlet means and thereby into the com bustion ai-r,

(c) a combustor housing comprising a confining toroid surface enclosing a volume within which compressed fuel-air mixture input is permitted to contact hot substantially completely burned gases present therein,

(1) said enclosing surface being directly exposed on one side thereof to the hot gases,

((1) a layer of solid insulation material covering the opposite side of said enclosing surface from said one side exposed to the hot gases to suppress the escape of heat from said volume,

(e) a first hollow annular conduit connected along the radially inward extent thereof in flow communication with said outlet means to receive compressed fuel-air flow exiting therefrom at high kinetic energy and being connected along the radially outward extent thereof in flow communication with said volume to introduce thereto at high velocity in a radial direction the compressed fuel-air flow so received, whereby the incoming fuel-gas mixture is thoroughly mixed with and heated by the hot burned gases in said volume,

(f) a turbine mounted adjacent said combustor housing,

(1) said turbine having inlet means, rotor means and exhaust means, and

(g) a second hollow annular conduit connected along the radially outward extent thereof in flow communication with said volume to receive burned gases exiting therefrom and connected along the radially inward extent thereof in direct flow communication with said turbine inlet means to direct radially inwardly thereto the burned gases so received.

'2. A power plant substantially as recited in claim 1 wherein the means for injecting fuel is a carburetor for introducing the fuel at low pressure.

3. A power plant substantially as recited in claim 1 in which the toroid surface is a hollow metal shell of substantially circular cross-section in any plane passing through the axis of symmetry and extending radially of the toroidal shape, said hollow shell having its curved inner surface substantially unobstructed to promote recirculation.

4. A power plant substantially as described in claim 1 wherein the fuel-air mixture from the introducing means enters the enclosed volume substantially tangential to the toroid surface.

'5. The improved power plant substantially as recited in claim 1 in which the volume wherein combustion occurs provides a residence time for the gases admitted thereto of at least about of a second at the design flow rate for the gases through said volume.

6. A power plant comprising in combination:

(a) a compressor,

(1) said compressor having circumferentially disposed outlet means and having inlet means for receiving all air entering said power plant,

(b) means connected to said inlet means for injecting fuel into said inlet means and thereby into all air during its entry,

() a combustor housing enclosing an annular volume within which compressed fuel-air mixture input is permitted to contact hot substantially completely burned gases resent therein in the absence of cooling means,

(d) a first hollow annular conduit connected along the radially inward extent thereof in flow communication with said outlet means to receive the total compressed fuel-air flow exiting therefrom at high kinetic energy and connected along the radially outward extent thereof in flow communication with said volume to introduce thereto at high velocity in a radial direction the total compressed fuel-air flow so received, whereby the incoming fuel-gas mixture is thoroughly mixed with and heated by the hot burned gases in said housing,

(e) a turbine mounted adjacent said combustor housing,

(1) said turbine having inlet means, rotor means and exhaust means, and

(f) a second hollow annular conduit connected along the radially outward extent thereof in flow communication with said volume to receive undiluted uncooled burned gases exiting therefrom and connected along the radially inward extent thereof in flow communication with said turbine inlet to direct thereto in the absence of cooling means the undiluted burned gases so received.

'1'. The power plant substantially as recited in claim 6 in which the volume wherein combustion occurs provides a residence time for the gases admitted thereto of at least about of a second at the design flow rate for the gases through said volume.

8. A power plant comprising in combination:

(a) a compressor,

(1) said compressor having circumferentially disposed outlet means and having inlet .means for receiving all combustion air entering said power plant,

(b) means connected to said inlet means for injecting fuel at low pressure into said inlet means and thereby into all combustion air entering said compressor,

(c) a combustor housing comprising a toroid surface enclosing an annularly-shaped volume Within which compressed fuel-air mixture input is permitted to contact hot substantially completely burned gases present therein in the absence of cooling means,

(1) said volume being large enough to provide a residence time of at least about 0.1 second at the design flow rate,

(d) a first hollow annular passage connected along the radially inward portions thereof in flow communication with said outlet means to receive the total compressed fuel-air flow exiting therefrom at high kinetic energy and connected along the radially outward portions thereof in flow communication with said volume to introduce thereto at high velocity in a radial direction the total compressed fuel-air flow so received,

(e) perforated means located in said volume for promoting recirculation, whereby the incoming total fuelgas flow is thoroughly mixed with and heated by the hot burned gases in said volume,

(f) a turbine mounted adjacent said combustor housing,

(1) said turbine having inlet means, rotor means and exhaust means,

g) a second hollow annular passage connected along the radially outward portions thereof in flow communication with said volume to receive undiluted uncooled burned gases therefrom and connected along the radially inward portions thereof in flow communication with said turbine inlet [means to direct thereto the burned gases so received.

9. A power plant substantially as recited in claim 8 wherein the means for injecting fuel at low pressure is a carburetor.

10. A power plant substantially as recited in claim 8 in which the combustor housing is a hollow metal shell of substantially circular cross-section in any plane passing through the axis of symmetry and extending radially of the toroidal shape, said hollow shell having its curved inner surface substantially unobstructed to promote recirculation.

11. A power plant substantially as described in claim 8 wherein the fuel-air mixture from the introducing means enters the enclosed volume substantially tangential to the toroid surface.

12. A method of burning fuel for the production of power in a power plant comprising the steps of:

(a) introducing a compressed mixture of fuel and air into the toroidal volume of a combustor housing at a velocity of at least about feet per second,

(b) providing a residence time for the gas flow through said volume of at least about 0.1 second to permit the mixing of hot substantially completely burned gases in said volume with the incoming compressed mixture to heat the gross gas mixture above the oxidation temperature of the fuel component to maintain combustion in the absence of a flame front, and below the temperature necessary to sustain a flame front, and

(c) conducting burned gas from said volume without dilution or cooling thereof below the oxidation temperature to a turbine rotor.

13. The method of burning fuel for the production of power substantially as recited in claim 11 wherein the temperature of the burned gas does not exceed about 1000 C. and a fuel is employed, which will not support a flame front at or below about 1000 C.

14. The method of burning fuel for the production of power substantially as recited in claim 11 wherein the mixture of fuel and air is non-flammable whereby it will not support a flame front.

15. A method of burning fuel for the production of power comprising the steps of:

(a) introducing a mixture of compressed fuel and compressed air into the toroidal volume of a combustor housing at high velocity,

(b) promoting recirculation of the incoming mixture with hot substantially completely burned gas present in said volume to heat the gross gas mixture above the oxidation temperature of the fuel component to maintain combustion in the absence of a flame front, and below the temperature necessary to sustain a flame front,

(c) causing gases entering said volume to remain therein for at least about 0.1 second, and

(d) conducting burned gas from said volume without dilution or cooling thereof below the oxidation temper-ature to drive a turbine rotor.

16. The method of burning fuel for the production of power substantially as recited in claim 15 wherein the temperature of the burned gas does not exceed about 1000 C. and a fuel is used, which will not support a flame front at or below about 1000 C.

17. The method of burning fuel for the production of power substantially as recited in claim 15 wherein the mixture of fuel and air is non-flammable whereby it will not support a flame front.

(References on following page) 9 1 5) References Cited by the Examiner 2,694,291 11/ 1954- Rosengart 6039.36

, 2,709,893 6/1955 Bil-man. UNITED STATES PATENTS 3,088,281 5/1963 Soltau 6039.72 X 2,595,505 5/1952 Bachle 6039.36 2,601,000 6/1952 Nerad 60 39.65 5 MARK NEWMAN, Primary Examiner. 2,678,615 5/1954 Soderlund 11028 RALPH SLEE, E i e 

1. A POWER PLANT COMPRISING IN COMBINATION, (A) A COMPRESSOR, (1) SAID COMPRESSOR HAVING CIRCUMFERENTIALLY DISPOSED OUTLET MEANS AND HAVING INLET MEANS FOR RECEIVING THE COMBUSTION AIR INPUT TO SAID POWER PLANT, (B) MEANS CONNECTED TO SAID INLET MEANS FOR INJECTING FUEL INTO SAID INLET MEANS AND THEREBY INTO THE COMBUSTION AIR, (C) A COMBUSTOR HOUSING COMPRISING A CONFINING TOROID SURFACE ENCLOSING A VOLUME WITHIN WHICH COMPRESSED FUEL-AIR MIXTURE INPUT IS PERMITTED TO CONTACT HOT SUBSTANTIALLY COMPLETELY BURNED GASES PRESENT THEREIN, (1) SAID ENCLOSING SURFACE BEING DIRECTLY EXPOSED ON ONE SIDE THEREOF TO THE HOT GASES, (D) A LAYER OF SOLID INSULATION MATERIAL COVERING THE OPPOSITE SIDE OF SAID ENCLOSING SURFACE FROM SAID ONE SIDE EXPOSED TO THE HOT GASES TO SUPPRESS THE ESCAPE OF HEAT FROM SAID VOLUME, (E) A FIRST HOLLOW ANNULAR CONDUIT CONNECTED ALONG THE RADIALLY INWARD EXTENT THEREOF IN FLOW COMMUNICATION WITH SAID OUTLET MEANS TO RECEIVE COMPRESSED FUEL-AIR FLOW EXISTING THEREFROM AT HIGH KINETIC ENERGY AND BEING CONNECTED ALONG THE RADIALLY OUTWARD EXTENT THEREOF IN FLOW COMMUNICATION WITH SAID VOLUME TO INTRODUCE THERETO AT HIGH VELOCITY IN A RADIAL DIRECTION THE COMPRESSED FUEL-AIR FLOW SO RECEIVED, WHEREBY THE INCOMING FUEL-GAS MIXTURE IS THOROUGHLY MIXED WITH AND HEATED BY THE HOT BURNED GASES IN SAID VOLUME, (F) A TURBINE MOUNTED ADJACENT SAID COMBUSTOR HOUSING, (1) SAID TURBINE HAVING INLET MEANS, ROTOR MEANS AND EXHAUST MEANS, AND (G) A SECOND HOLLOW ANNULAR CONDUIT CONNECTED ALONG THE RADIALLY OUTWARD EXTENT THEREOF IN FLOW COMMUNICATION WITH SAID VOLUME TO RECEIVE BURNED GASES EXITING THEEREFROM AND CONNECTED ALONG THE RADIALLY INWARD EXTENT THEREOF IN DIRECT FLOW COMMUNICATION WITH SAID TURBINE INLET MEANS TO DIRECT RADIALLY INWARDLY THERETO THE BURNED GASES SO RECEIVED.
 15. A METHOD OF BURNING FUEL FOR THE PRODUCTION OF POWER COMPRISING THE STEPS OF: (A) INTRODUCING A MIXTURE OF COMPRESSED FUEL AND COMPRESSED AIR INTO THE TOROIDAL VOLUME OF A COMBUSTOR HOUSING AT HIGH VELOCITY, (B) PROMOTING RECIRCULATION OF THE INCOMING MIXTURE WITH HOT SUBSTANTIALLY COMPLETELY BURNED GAS PRESENT IN SAID VOLUME TO HEAT THE GROSS GAS MIXTURE ABOVE THE OXIDATION TEMPERATURE OF THE FUEL COMPONENT TO MAINTAIN COMBUSTION IN THE ABSENCE OF A FLAME FRONT, AND BELOW THE TEMPERATURE NECESSARY TO SUSTAIN A FLAME FRONT, (C) CAUSING GASES ENTERING SAID VOLUME TO REMAIN THEREIN FOR AT LEAST ABOUT 0.1 SECOND, AND (D) CONDUCTING BURNED GAS FROM SAID VOLUME WITHOUT DILUTION OR COOLING THEREOF BELOW THE OXIDATION TEMPERATURE TO DRIVE A TURBINE ROTOR. 